Nonreciprocal transmission of electromagnetic waves with nonlinear active plasmonic metasurfaces

Nonreciprocity is important for optical information processing, full-duplex communications, and protection of sensitive laser equipment from unwanted reflections. However, it very challenging to obtain strong nonreciprocal response in frequencies, especially when nanoscale configurations are considered. In this work, we solve problem by demonstrating a compact bifacial plasmonic metasurface that acts as new ultrathin transmission filter at near-infrared frequencies. The proposed nanostructure simple be practically implemented, since composed two silver nanostripes with different dimensions placed on both sides an active dielectric spacing layer. introduced gain leads exceptional point formation the linear operation regime, where unidirectional perfect due loss compensation achieved presented non-Hermitian parity-time symmetric system. demonstrated breaks Lorentz reciprocity law its nonlinear considered, mainly spatially asymmetric geometry combined enhanced nonlinearity. Strong broadband nonreciprocity unity contrast opposite directions realized under relatively low input intensity values. Furthermore, third harmonic generation pronounced also illustrated same design. findings work can lead realization various self-induced nanophotonic configurations, such integrated ultrafast switches, protective coatings, directional imaging devices.